Digital electronic systems, e.g., computer systems, often need to communicate using different interfaces, each running at an optimized speed for increased performance. Typically, multiple clock signals having different frequencies are utilized for providing appropriate timing to the interfaces. Further, the frequencies of such clock signals are generally related to one another in a predetermined manner. For example, a core or system clock running at a particular frequency (FC) may be utilized as a master clock in a typical computer system for providing a time base with respect to a specific portion of its digital circuitry. Other portions of the computer system's digital circuitry (such as a bus segment and the logic circuitry disposed thereon) may be clocked using timing signals derived from the master clock wherein the derived frequencies (FD) follow the relationship: FC/FD≧1.
Because of the asynchronous—although related—nature of the constituent digital circuit portions, synchronizer circuitry is often used in computer systems to synchronize data transfer operations across a clock domain boundary so as to avoid timing-related data errors. Such synchronizer circuitry is typically required to possess low latency (which necessitates precise control of the asynchronous clocks that respectively clock the circuit portions in two different clock domains). Typically, phase-locked loops (PLLs) are utilized in conventional synchronizer circuitry arrangements to produce clocks of different yet related frequencies. The PLLs may have a large amount of input/output (I/O) jitter that results in low frequency phase difference, or skew, between different clocks of the synchronizer circuitry. Accordingly, it is essential to determine the skew between different clocks of the synchronizer circuitry.